i need help with a freind i like..

ok, so there is a girl who iive become pretty close freinds with,we joke and laugh and have a good time, and im beggining to feel more for her recently. when im cutting up with freinds i have a very loud, almost immature side that comes out, and i dont think many people who just know me as a freind know that i have a very sweet side that comes out in my relationships with girls. I geuss im just worried that if i start acting around her the way i would around a girl im interested in, i would creep her out, but my "just freinds" attitude is in no way sexy, and i do want to let her on some and not just ask her out. so please help with how i should go about this somewhat akward situation